1. Field of the Invention
The present invention generally relates to methods and systems for measuring the position of an in vivo radio device, such position measuring devices, and in vivo radio devices, and specifically relates to such a method and system for measuring the position of the in vivo radio device based on receiving characteristics of position measuring signals.
2. Description of the Related Art
Endoscopes have long been used as medical devices for acquiring in vivo information and taking it to the outside. The endoscope is a camera mounted at an end of a cable. The camera takes pictures of a selected place (e.g., a diseased part) in a human body, and transmits the pictures via the cable to display them on a monitor device outside of the human body. However, the camera has to be swallowed and the cable has to be moved around in the human body to carry the camera to the selected place, and therefore a great burden is imposed on the patient.
In order to mitigate the burden on the patient, it was envisaged that electromagnetic waves can be used for transmitting vital information acquired in the human body to the outside. In this scheme, a patient swallows a small-sized capsule endoscope with a built-in camera. This ingested capsule endoscope moves in the patient's body and takes pictures of the gastrointestinal tract in response to control signals transmitted from outside of the patient's body. The pictures taken are transmitted from the capsule to a monitor device outside of the patient's body by RF, and displayed on the monitor device. One good example of such capsules is published on the Internet Website at www.rfnorika.com with a title “Endoscope Capsule NORIKA System”.
When doctors use such pictures or images displayed on the monitor to diagnose, it is essential for them to know precisely where in the patient's body the images were taken or where the administered capsule is located in the patient's body at present.